Positive-ion bombardment of a graphite cathode in a low-pressure glow discharge is used to heat the cathode to temperatures in excess of 2000°C. A magnetic field of a few hundred Gauss used in a magnetron configuration reduces lamp voltage and permits operation at less than 1 kV
with cathode current densities greater than 350 mA/cm2. A solution residue sample deposited on the 1.6-mm-diameter graphite cathode is atomized in about one second. The atomic vapor is excited in the glow discharge near the cathode surface. The effects of pressure and magnetic field
strength on furnace performance are described. At low furnace temperature, plasma current conduction is by electrons produced by positive ion bombardment of the cathode surface. At higher temperatures, current conduction is largely by thermionic electrons.
Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109
Publication date: August 1, 1989
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